The present invention relates to panel saws in general and, in particular, to a method for feeding panels to a panel saw machine.
In the furniture industry, panel saw machines are used to cut large rough-hewn panels to obtain suitably shaped smaller, semi-finished or finished panels.
Before being cut, the panels are stacked on a loading table on the panel saw machine so as to form regular geometrical stacks, in which the number of panels corresponding with a precise cutting pattern is selected according to the number of items of furniture to be produced.
The stacks which are gradually formed on the loading table on the machine are obtained from a large stack located at a loading station further upstream and on a feed line which comprises, one after another, the loading station, the loading table and the cutting station of the panel saw machine.
The rough-hewn panels are essentially fed from the loading station to the loading table on the panel saw machine using two different pick up and transfer techniques. The first envisages moving the various panels by means of sliding, transversal to the stack, of the top panel, which is translated resting on the panel immediately beneath it. In contrast, the second technique envisages the pick up and transfer of the panels which reach the top of the stack, using vacuum pick up means.
In the technique which envisages the sliding of the panels resting on the stack, the panels are picked up and transferred following a preparatory stage during which the panel to be transferred is first lifted slightly above the stack, using vacuum pick up means applied to one side of the panel. The panel is then intercepted by a horizontally mobile mechanical pusher, which pushes it and feeds it along the feed line, the panel resting on the stack until it arrives at an infeed device, preferably of the type with rollers positioned opposite one another.
The infeed device transfers the panels received and sends them in series over the loading table on the panel saw machine. When the panels reach the upright of the loading table, they are released by the infeed device and drop, under their own weight, being deposited one on top of another on the loading table, where suitable aligning means tidy the stack as it is formed.
When the preset number of panels is present in the stack, suitable transfer means transfer the stack to the panel saw machine for machining.
With the infeed technique that uses the vacuum pick up means only, the individual panels are first picked up from the top of the stack, until they are completely separated from it, then transferred by a mobile carriage, which mounts the pick up means, over the loading table on the panel saw machine, where they are allowed to drop under their own weight.
The two operating methods described above each have a specific field of application. The technique which envisages sliding of the panels is used almost exclusively for very thick panels, which are intrinsically rigid. In contrast, the specific application of the technique envisaging panel pick up and transfer using vacuum means is for feeding thin, highly flexible panels.
The basic disadvantage of such solutions is that they require total cycle times which are negatively affected by the operating times of the vacuum pick up systems, although to different degrees in the two above-mentioned solutions.
This disadvantage is particularly noticeable when feeding thin panels to panel saw machines set up to perform fairly simple cutting patterns. In this case, since the panel saw machine can carry out high speed machining, in less time than is required to form the stack of panels to be fed into it, the resulting disadvantage is discontinuous machining by the panel saw machine, since it cannot be continuously fed and so must stop to await the arrival of new panels.
Another disadvantage of both solutions is that only one panel at a time can be picked up and transferred from the stack; again, this means that the panel saw machine may have to wait until formation of the stack of panels to be machined is completed.
A further disadvantage is the fact that, at present, panel saw machines are fed using systems that are structured to function according to one technique or the other, meaning that it is not normally possible to pick up and transfer rigid and thin panels on the same feed line. To overcome this disadvantage, some known systems envisage the use of twin feed devices, structured according to one pick up and transfer technique or the other, alternating in their operation on the feed line, depending on the type of panels to be fed. However, due to the more complex construction and control, this solution is not always economically feasible.
The aim of the present invention is, therefore, to overcome the above-mentioned disadvantages.
In accordance with the present invention, said aim is achieved by a method for feeding panels to a panel saw machine which comprises a transfer step during which the panels of a vertical stack are transferred in series from the top of the stack to a loading table on the panel saw machine. The transfer step comprises a translation of the panels along a feed line, the initial section of which is covered by the panels, pushed by a horizontally mobile pusher, until they arrive at an infeed device with opposite rollers. A final section of the feed line, between the infeed device and the loading table on the panel saw machine, is covered by the panels under the action of the infeed device. The method is characterised in that the pusher element and vertical stack perform a relative translation, transversal to the feed line, involving movements whose extent is controlled by control means, so as to allow the pusher element to make contact with one or more panels forming packs of panels, positioned one on top of another, determined according to the extent h of the translation, and transfer them from the stack.